The first ionisation enthalpy `(Delta_(i)H^(o-))` values of the third period elements, `Na, Mg` and `Si` are respectively `496, 737` and `786 kJ mol^(-1)`. Predict whether the first `Delta_(i)H^(o-)` value for `Al` will be more close to `575` or `760 kJ mol^(-1)`? Justify your answer.

Options

A. 350
B. 860
C. 575
D. 1125

Answer

C

Explanation

The first ionisation energy of AI is greater than Na but less than Mg so the value must be less than 737 and greater than 496 i.e., 575.